Motor-control system



E.YS..LAMMERS, JR.

MOTOR CONTROL SYSTEM.

APPLICATION FILED JUNE 13, 1917 1 ,392,255 PatentedSept. 27, 1921.

3 SHEETS-SHEET I.

75 EXc/f'er WITNESSES: INVENTOR y BY I 2 ATTORNEY E. s. LAMMERS, JR.MOTOR CONTROL SYSTEM.

APPLICATION FILED JUNE 13, I917. 1,392,255. PatentedSept- 27, 1921,

' 3 SHEETS-SHEET 2.

WITNESSES: INVENTOR Edwin S. Lammers, Jr.

i madiowzi m E. S LAMMERS, JR. MOTOR-CONTROL SYSTEM.

APPLICATION FILED JUNE 13, 1911. I PatQIIitBdSGPt' 27, 1921.

3 SHEETS-SHEET 3- WITNESSES INVENTOR a. 4 [dw/n Slammers, J25

EDWIN S. LAMMERS, JR, OF-WILKINSBURG, YENNSYLVA'NIA, ASSIGNOR TO WEST-INGHOUSE ELECTRIC & MANUFACTURING COMYANY, A. CORPORATION OF PENN-SYLVANIA.

Moron-common SYSTEM.

Application filed June 13,

T 0 all whom it may concern:

Be it known that I, EDWIN S. LAMMERS, Jr., a citizens of the UnitedStates, and a resident of Wilkinsburg, in the county of Allegheny andState of Pennsylvania, have invented a new and useful Improvement inMotor-Control Systems, of which the following is a specification.

. My invention relates to motor-control systems and it has for itsobject to provide a simple and effective arrangement for insuring theoperation of a series of electromagnetically operable switches in apredetermined sequence.

My invention comp-rises a series of roressively actuated switches, eachof w ich 18 provided with a pair of coils of substantially equalampere-turns. It is necessary that both coils of any switch shall beenergized in order to effect the closing of the switch, Either of thecoils, when energized, exerts a pull that is sufficient to retain theswitch in its closed position.

A series of switches arranged in the manner described above may beemployed in various ways. For example, they may be embodied in a s stemfor controlling the field excitation o dynamo-electric machines employedin connection with reversing blooming mills for rolling steel. They mayalso be employed in connection with electric motors for operating minehoists or other machines in which it is desirable that the controllingswitches operate in a predetermined sequence either automatically or inaccordance with the position ofa manually operable controller.

In the accompanying drawings, Figure 1 is a diagrammatic view of themain and field circuits of a generator and an electric motor such asareemployed in connection with steel mill operations. Fig. 2 is a chartindicating the sequence of operation of the various switches of thesystem shown in Fig. 1. Fig. 3 is a diagrammatic .view of circuits andapparatus illustratin my invention applied to the circuits 0 an electricmotor. Fig. 4 is a diagrammatic view of the circuits and apparatus forcontrolling the various switches shown in the system of Fig. 1. Fig. 5is a diagrammatic View of a series of switches arranged in accordancewith my invention for automatically controlllng the c rcuits of anelectrlc motor.

Specification of Letters Patent.

Patented Sept. 27, 1921. 1917. Serial No. 174,439.

Fig. 6 is a schematic arrangement of the principal circults of thesystem shown in Fig. 5.

eferring particularly to Fig. 1, a generator G and a motor M connectedin a closed circuit. The generator G is provided with a field-magnetwinding 1. The circuit of the field-magnet 1, which comprises a resistor2, is controlled by reversing switches 3, 4, 5 and 6 and by a series ofprogressively actuated switches 7, 8, 9 and 10. The motor M is providedwith a field-magnet winding 12 which is in circuit with a resistor 13.The resistor 13 is controlled by a second series of progressivelyactuated switches 14, 15, 16 and 17.

Reference may now be had to Fig. 4, in which the circuits and apparatusforcontrolling the several switches embodied in the system of Fig. 1 arediagrammatically switch, when closed, may be retained in that.

position when either of the coils is energized. The coils 18 arearranged to be energized in order in accordance with the position of themanually operable master switch or conare permanently troller 20. Thecircuits of the respective coils 18 are arranged to be controlled by thepreceding switch to close in order that the switches may close in thepredetermined sequence regardless of the rate at which the controller 20is actuated to its full running position. The coils 19, which areconnected in parallel circuit relation to each other, are arranged to beenergized simultaneously.

Current for the various control circuits and for supplying energy to therespective field-magnet win ings of the generator and of the motor isfurnished b an exciter generator E. The circuits 0 switches 7, 8, 9 and10 are controlled by a relay 22 having an actuating .coil 23 which isconnected, by means of conductors 24 and 25, across the terminals of aresistor 26 that is in series-circuit relation with the generthe coils19 of ator and the m to ametnrewindin s. The

relay 22 accordingly controls the circuits of the coils 19 in accordancewith the value of the current traversing the main circuit.

The effect of the operation of the relay 22 is controlled by a relay 27which normally occupies its illustrated osition. The relay 27 iscontrolled by a 0011 28 that is in series with the coils 18 of switches7, 8, 9 and 10 and is energized in accordance with the number of coils18 that are connected in circuit by the controller 20. The relay 27 iscontrolled also by a coil '29 which is connected by means of conductors30 and 31 across the terminals of the generator G. The coil 29 opposesthe force of the coil 28 with a force t at is proportional to the valueof the voltage of the generator G.

A spring 32-tends to retain the relay 27 in its illustrated position.During the operation of the controlling switches, the position of therelay is dependent upon the value of the voltage of the generatorcorresponding to the portion of the resistor 2 which is in circuit, asdetermined by the position of the controller 20, relatively to theactual voltage of the generator as measured by the degree to which thecoil 29 is energized. The coils 28 and 29 tend to actuate-the relay 27in opposite directions.

A relay 34, which is similar to the relay 22, controls the circuits ofthe coils 19 of the switches 14, 15, 16 and 17. The relay 34 is providedwith an actuating coil 35 that is connected across the terminals of theresistor 26. The efi'ect of the operation of the relay 34 is controlledby a relay 36 which normally occupies its illustrated position.

The relay 36 comprises actuating coils 37 and 38 which respectively tendto actuate the switch toward and from the position in which it isillustrated. The coil 37 is connected in series with the coils 18 of theswitches 14, 15, 16 and 17. The coil 37 is accordingly energized to adegree depending upon the number of coils 18 that are incircuit.

The coil 38 is connected, by'means of constationary. When the variousrelays and switches occupy their respective illustrated positions, acontrol switch 44 is closed and the coils 19 or the switches 7, 8 and 9are energized by a circuit which extends from the positive terminal ofthe exciter E through a port on of conductor 43, relays 27 and 22, coils19, which are in parallel relation, and switch 44 to the negativeterminal of the exciter. The coils 18 of these switches are denergizedbecause their respective circuits are open at the master controller.

The corresponding coils 19 of the switches 14, 15, 16 and 17 areenergized by a circuit which extends from the positive terminal of theexciter E through a portion of conductor 43, relays 36 and 34, coils 19,which are in parallel relation, to the negative terminal of the exciter.The switches 14, 15, 16 and 17 are closed when the controller is in itsoff position. When the switch 10 is open, a circuit for the coil 18 ofswitch 14 is completed which extends from the positive ter minal of theexciter E through an interlock connected to switch 10, coil 18 of switch14 and coil 37 to thenegative terminal of the exciter.

Since both the coils 18 and 19 of switch 14 are energized, this switchcloses to complete a shunt circuit for the corresponding section of theresistor 13. The coils 18 of switches 15, 16 and 17 are respectivelycontrolled by interlocks connected to the preceding switch to close, andthe closing of switch 14 accordingly effects the closing of switches 15,16 and 17 in the order named. The major portion 'of the resistor 13 isshunted by these switches and the motor is provided with a strongmagnetic field for starting.

An interlock connected to switch 17 completes a circuit for connectingthe coil 38 across the terminals of that section of the resistor 13 thatis not controlled by the switches 14, 15, 16 and 17. The coil 38 isenergized to a maximum degree because the value of the field current isa maximum. The force of the coil 38 predominates over that of the coil37 and the spring 41 and the relay is overbalanced. It assumes its otheroperative position in which the coils 19 of the switches 14, 15, 16 and17 are deenergized so long as the relay 34 remains in its illustratedposition.

To accelerate the motor in the forward direction, the controller 20 isactuated to the left. as viewed in Fig. 4. When the controller occu iesposition a, a circuit is completed whic extends from the positiveterminal of the exciter through conductor 43, controller 20, interlock45 of switch 3, actuating coils of reversing switches 4 and 6 and coil28 of rela 27 to the negative terminal of the exciter As best shown inFi 1, the closing of the switches 4 and 6 estab ishes a circuit for thefield-magnet winding 1 of the generator which extends from the positiveterminal of the exciter, through switch 4, resistor 2, field-magnetwindin 1 and switch 6 to the negative terminal 0 the exciter,

In position b of the controller 20, a circuit terminal of the exciter,through conductor 46, interlock connected to switch 6, coil '18 ofswitch 7 and coil 28, to the negative terminal of the exciter. Theswitch 7 is now closed since both of its operating coils 18 and 19 areenergized.

The closing of switch partly completes a circuit for the actuating coil18 of switch 8 and the latter switch closes when the controller isactuated to the succeeding position 0. The switches 8, 9 and 10accordingly close in order as the controller is actuated to itssuccessive positions 0, d and .2. Substantially the entire resistor 2 isshunted and the voltage out the generator has increased to acorresponding degree. Each of the switches 8, 9 and 10, upon closing,completes a holding circuit for the coil 18 of the preceding switch toclose and the switch 7,

upon closing, completes a holding circuit for the coils of the reversingswitches. The innction of these holding circuits is to control thesequential operation of the switches during deceleration.

Upon the closing of switch 10, an interlock 47, which is mechanicallyconnected thereto, opens the circuit previously traced for the coil- 18of switch 14.. The latter switch does not open, however, because aninterlock connected to switch 15-controls the holding ci cuit for thecoil 18. The actuation of the controller to position f efiects the.

opening of the holding circuit for coil 18 of switch it through theinterlock connected to switch 15. there is one less coil 18 in circuitwith the coil 37, the force of the coil 3?. is overhalanced by that ofthe coil 38, causing the relay 36 to open, thereby to open the circuitsof the coils 19. The switch 14 opens to insert the corresponding sectionof the resistor 13 in series with the field-magnet winding 12 to furtheraccelerate the motor. The actuation of the controller to its succeedingpositions effects the opening of switches 15, 16 and 17 in order tofurther weaken the field of the motor and thereby eiiect itsacceleration to its normal speed.

The operation of the system has been described upon the assumption thatthe controller 20 is actuated in astep-by-step manner from its oilposition to its full running position. in actual practice, however, thecontroller 20 may be actuated from the one position to the other by acomparatively quiet: continuous movement. In such case, operation of thereversing switches 4- switches 7, 8, 9 andlO occurs in the orderdescribed v 27, which controls the cir- .1 e not operate to interruptthe circuit 1 ot the c i s 18 heean e coils 18 of the latter group ofcircuit is such that the coil 28 is energized" to maintain the relay inits illustrated position. The generator voltage does not increasesimultaneously with the o eration of the switches for increasingthe eldexcitation of the generator.

The switches 14, 15, 16 and 17 open in order upon the closing of switch10 since the holding circuits for the coils 18 of these switches areopened at the controller 20, and these coils are accordingly deenergizedin order upon the opening of the preceding switch. The opening of switch17 opens the shunt circuit for a section of resistor 13 and the coil 38is accordingly deenergized. The coil Shisdenergized also since none ofthe coils 18 of the'latter groupof switches are in circuit. The relay 36accordingly as sumes its normal position to complete circuits fortheceils 19 in preparation for the closing of the switches.

The operation of the switches described above occurs withoutinterruption in case the current traversing the main circuit of themotor andthe generator does not exceed a predetermined value. In case,however, the voltage of the generator is increased at such rate that thecurrent traversing the main circuit exceeds the predetermined-value, thecoil 23 is energized-to open the relay 22 and thereby open the circuitsof the coils 19 of switches '8, 8,9 and 10.

They switches that are closed remain in this position because thecorresponding coils 18 exert a pull that is sufiicient to retain them inthe closed positions. The relay 22 occupies its open position so long asthe current traversing the main circuit excoeds the predetermined value,and the operation of the switches is accordingly interrupted for acorresponding period. When the current falls to the predetermined value.the relay 22 closes and the closing of the switches continues in orderunless the current again exceeds the predetermined value. In the samemanner, the operation of the switches 1 15, 16 and 17 is interrupted bythe operation of relay 34 in casethe coil 35 is suiiiciently energizedto actuate the relay to its upper position. When the relay 34; cccupiesits upper position, the circuits of the coils 19 are completed throughthe relay 36, and the opening of the switches to insert the resistor 13in se ies with the field-magnet winding 12 is interru ted until thecurrent traversing the main circuit falls to the pre determined value.

lit will he readily understoodthat the controller he actuated to itslull runnin position by a continuous movement and that the operation ofthe system will occur automatically. operation of the controllingswitches is, interrupted automatically upon the occurrence of abnormalcurrent conditions, but the operation of the switches is resumed whennormal conditions again obtain. The voltage of the generator is thusincreased and the field excitation of the motor is decreased at suchrates that the motor is accelerated at a maximum rate consistent withsafety.

To decelerate the motor, the controller is actuated toward its oiiposition. When the controller occupies position It, thecoil 18 of switch17 is again energized by means of a circuit which comprises the coil 37of relay 36. The coils 19 of the motor controlling switches areenergized when the relay occupies its illustrated position.

The switch 17 accordingly closes to complete a shunt circuit for thecorresponding section of resistor 13. The closing of switch 17 completesthe circuit of coil 38 and, when the current traversing the fieldcircuit of the motor reaches a value corresponding to the adjustment ofthe controller, the coil 38 predominates and the relay 36 is actuated toopen the circuit of the coils 19.

When the controller occupies position g, the coil 18 of switch 16 isenergized and the coil 37 of relay 36 again predominates to actuate therelay to its illustrated position and thereby complete a circuit for thecoils 19, whereupon the switch 16 closes. The operation of the relay 36occurs between the closing of the successive switches in order toprevent the shunting of the resistor at a rate faster than that at whichthe field current increases.

When all of the motor controlling switches are closed, the motoroperates with a field maximum strength and its speed is accordinglydecreased. The closing of switch 14 opens the holding circuit of c011 18of switch 10 and restores the control of the latter switch to thecontroller 20.

hen the controller occupies position d, the coil 18 of switch 10 isdeenergized and the pull exerted by the coil 28 is decreased to acorresponding degree. The force exerted by the coil 29 is a maximumsince the enerator voltage is at its normal value. The coil 29predominates and the relay 27 is accordingly actuated to its otheroperative position to open the circuits of the coils 19 that arecontrolled by it. The switch 10 accordingly opens to insert thecorresponding section of resistor in circuit with the generatorfield-magnet winding.

The coil 29, of relay 27 predominates so long as the generator voltageexceeds the value corresponding to that for which the controller isadjusted. If the generator controlling switches are opened at arelatively rapid rate, the generator voltage is reduced to a value belowthat of the motor and the latteroperates as a generator. If the curspeedof the motor is decreasing tends to maintain the current traversing themain circuit at a maximum value and the speed of the motor isaccordingly decreased at a maximum rate.

The operation of the motor in the reverse direction is effected byactuating the controller to the right, as viewed in Fig.4.

eversing switches 3 and 5 operate to complete the circuit of generatorfield-magnet winding 1 with the connections of the latter reversed withrespect to the terminals of the exciter E. The operation of the severalswitches and relays differs in no material respect from that describedin connection with the operation of the motor in the forward direction.

It will be noted that, in the system illustrated in Figs. 1 and 4, Irovide a series of progressively actuated switches for controlling therespective field circuits of an electric generator and an electricmotor. Each of the switches is provided with a pair of actuating coilsboth of which must be energized to effect the closing of the switch andeither or which, when energized, retains the switch in its closedposition.

()ne member of each pairof coils is controlled by a manually operablemaster switch and by the preceding and succeeding switches to operate.The other coils are controlled simultaneously by a relay that isactuated in accordance with the value of the current traversing the maincircuit comprising the motor and the generator armatures.

The effect of the operation of this relay is controlled by a secondrelay having coils which tend to actuate it in opposite directions. Oneof the coils is energized in accordance with the number of operatingcoils connected in circuit by the master switch. In the case of theswitches for controlling the field circuit of the generator, the secondcoil is connected across the terminals of the generator. Thecorresponding relay is accordingly controlled in accordance with theactual generator voltage relatively to the value of the voltagecorresponding to the adjustment of the controller.

In the case of the relay which coacts with the switches for controllingthe motor field circuit, one of the opposing coils is connectedsucceeding switches to close.

in series with the coils controlled by the master switch and the othercoil is so connected as to be energized in achordance with the currenttraversing the field circuit of the motor. This relay operates,therefore, in accordance with the actual value oi the current traversingthe motor field circuit relatively to the value of the currentcorresponding to the adjustment of the master switch.

Reference may now be had to Fig. 3, in which a modification of myinvention is diagrammatically illustrated. Line conductors 51 and 52supply current to an electric motor, the armature of which is indicatedat 53 and which has a shunt field-magnet winding 54. A starting resistor55 is controlled by a series of progressively actuated switches 56, 57and 58."

Theswitches 56, 57 and 58 are respectively provided with actuating coils59 and 60, both of which must be energized to eifect the closing of theswitch, but either of which exerts a pull of sufficient strength tovmaintain the switch in its closed position. The motor circuit iscontrolled by an electromagnetically operable line switch 61; Aninterlock 62 connected to the line switch 61controls the circuits of thecoils 60. A relay 63, having a coil 64 in series with the motorarmature, controls the circuits of the coils 59. A master switch 65controls the operation of the several switches.

To start the motor, the controller is actuated to the left, as viewed inFig. 3. In position a, the coil 66 of line switch 61 is energized andthe latter closes to complete the armature circuit of the motor throughresistor 55. The interlock 62 partially completes the circuits of therespective coils 60.

In position b of the master switch, the coils 59 and 50 of switch 56 areenergized and the switch 56 accordingly closes. The closing of switches57 and 58 is effected upon the actuation of the master switch 65 to itssucceeding positions.

The closing of the switches in the order named is insured by theprovision of interlocks connected to the switches 56 and 57 forcontrolling the circuits of the coils of the The master switch mayaccordingly be actuated from its illustrated position to its fullrunning position by a rapid movement. The switches then close in orderin case the current traversing the motor circuit does not exceed apredetermined value. In case the current traversing the motor circuitreaches a value at which the coil 64 is energized to operate the relay63, the several coils 59, which are energized upon the actuation of themaster switch 65 to its full running position, are deenergized. If, for

example, the switch 56 is closed, tne operation of the relay 63 does notefi'ect the openbe controlled either manually by the adjust- I ment ofthe master switch 65 to its running position in a step-hy-step manner orthe operation may occur automatically upon the actuation of the masterswitch to its full running position. While the operation of the motor isarranged i'or one direction only,

it will he understood that my invention is applicable equally as well tosystems in which reversing mechanism is embodied for the purpose ofoperating the motor in opposite directions.

Referring now to Fig. 5, a second modification of my invention embodiesan arrangement which operates automatically to accelerate an electricmotor when such action is initiated upon the operation of a manuallyoperahle master switch. An electric motor 69 has aseries field-magnetwinding 70 and a shunt field-magnet winding 71. The armature circuit ofthe motor is controlled hy reversing switches 72, 73, 74 and 75. Astarting resistor 76 is controlled by switches 77 and 78, each of whichis provided with a pair of operating coils similarin all materialrespects to the corresponding coils of the systems previously:described. The motor circuit is controlled by an electromagneticallyoperable line switch 79. The control circuit is controlled by a masterswitch 80 and a low-voltage relay 81 which is closed when the masterswitch occupies its 05 position-and a control switch 82 is closed.- Tostartthe motor, the master switch 8 may be actuated, for example, in aclockwise direction, as viewed in Fig. 5, for the operation of the motorin the forward direction. A circuit is completed which extends from thepositive side of control switch 82,

through overload relay 83, low-voltage relay I 81, master switch 80,coils of reversing switches 75 and 73, actuating coil of line switch 79, and overload'relay 84, to the negative side of the control switch 82.The re- 'versing switches 7 3 and 75 close to complete the armaturecircuit of the motor, and line switch 77, and accelerating rela 87, tothe negative terminal of the contro switch 82. A second circuit, whichis completed by the interlock 85, extends through coils 88 and 89.

The switch 77 is closed since both coils 86 and 88 are energized. Theclosin of switch 77 completes a circuit for a 0011 90 I terrupted by theaccelerating relay 87, the

actuating coil of which is in series with the armature of the motor. Theaccelerating relay 87 is adjusted to operate when the current traversinthe motor circuit corresponds to the normal load value. 'The'closin ofswitch 78 shunts the actuating coil 0 the rela 87.

T e operation of overload relays 83 and 84, which are adjusted forabnormal current values, efi'ects the opening of the reversing switches,the line switch 79, low-voltage relay 81 and switches 77 and 78. It isthen necessary to return the master switch 80 to its oli' position toagain initiate the starting operation.

I claim as my invention: V a

1. In a motor-control system, the combination with a generator and amotor in series circuit relation, each of said dynamoelectric machineshaving a field-magnet winding, and a resistor in circuit with each ofsaid field-magnet windings, of means for controlling said resistors,said means comprising a plurality of electro-magnetically operableswitches each of which is provided with a pair of magnet coils .both ofwhich must be energized to close the corresponding switch, and means forinsuring theener 'zation of one member of each pair of coil; in adefinite sequence. a

2. In a motor-control system, the combination with a plurality ofprogressively actuated switches, of a air of operating coils for each ofsaid switches, both of which must be energized to effect the closing ofthe corresponding switch, either of said coils being effective to retainsaid switch in its closed position, means for collectively controllingcorresponding coils of each pair and means for selectively controllingother coils of each pair. p

3. In a motor-control system, the combination with a plurality ofprogressively actuated switches, of a pair of operating coils for eachof said switches both of which must be energized to e'fi'ect the closingof the corresponding switch, either of said: coils being effective toretain said switch in its closed position, said coils and said switchesbeing so connected as to insure the opening and the closing of saidswitches in a predetermined sequence, and means for-initiating theoperation of said switches.

42. In a motor-control'system, the combination with a plurality ofprogressively actuated switches, of a pair of o eratin coils for each ofsaid switches both 0 which must be energized to effect theclosing of thecorresponding switch, either of said coils being effective to retainSaid switch in its closed position, one member of each pair of coils,except that for the first switch to operate, being controlled by theprecedin switch to operate, a controller for the sai members of thepairs of coils, and automatic means for controlling the energization ofthe other coils. I

5. In a motor-control system, the combination with a dynamo-electricmachine and a plurality of progressively actuated switches operativelyassociated therewith, of a air of operating coils for each of said switces, the circuit of one member of each pair of coils beingv controlled bythe receding switch to operate, manually opera le means for controllingsaid circuits, and means for controlling the circuits of the other coilsin accordance with the value of the current with said master switch,each of said coils except that for the first of said switches to switchto operate, and each of said coils except that for the last of saidswitches to close being controlled by the succeeding switch to operate.

7. In a motor-control system, the combination-with a dynamo-electricmachine and a plurality of progressively actuated switches operativelyassociated therewith, of a pair of operating coils for each of saidswitches, the circuit of one member of each pair of coils 'beingcontrolled by the preceding switch to operate,imanually operable meansfor controlling said circuits, automatic means for controllin theother'members of said pairs of coi s in accordance with the value of thecurrent traversing said dynamo-electric machine, and means forcontrolling the effect of the operation of said automatic means.-

8. In a motor-control system, the combination with a dyanmo-electricmachine and a plurality of progressively actuated traversing the circuitof said dynamo-electric I a master switch, an actu- .close beingcontrolled by the preceding switches operatlvely associated therewith,of

cuit and a plurality of progressively actuated switches for controllingthe same, of a pair of operating coils for each of said switches,manuall operable means for controlling one member or each pair of coils,a relay for automatically controlling the other coils in accordance withthe value of the current traversing said circuit, and a second relay forcontrolling the efiect of the operation of the ether relay in accordancewith the actual circuit conditions produced by said manually operablemeans relatively to the circuit conditions corresponding to theadjustment of said manually operable means.-

10. In a motor-control system, the combination with a dynamo-electricmachine and a plurality of progressively actuated switches operativelyassociated therewith, of a pair of operating coils for each of saidswitches, manually operable means for controlling one member of eachpair of coils, and means for controlling the circuits of the other coilsin accordance with the value of the:v current traversing the circuit ofsaid dynamo-electric machine and in accordance with the actual voltageconditions obtaining in the circuit of said dynamo-electric machinerelatively to the voltage conditions corresponding to the adjustment ofthe manually'operated means.

11. In a motor-control system, the com bination with an electric circuitand a plurality of progressively actuated switches for controlling thesame, of a pair of operating coils for each of said switches,manuallyoperable means for controlling one member of each pair of coils,and means comprising a relay for controlling the other coils, said relayhaving opposing coils one of which is in series with the coilscontrolled by the manually operable means and the other of which isenergized in accordance with the value of the current traversing saidcircuit.

12. The combination with an electromagnetic switch having a pair ofactuating coils, of a switch in circuit with one of said coils andhaving an actuating coil in circuit with said other coil.

13. The combination. with a dynamo-electric machine and a plurality ofswitches for controlling said machine and having actuating coils inparallel relation to each other, of a switch for controlling theoperation or said switches and having an actuating coil in series withsaid first=named coils.

14. The combination with a dynamo-elec trio machine having a resistorassociated therewith, of a switch for controlling said resistor andhaving two actuatingcoils, a pair of double-throw switches adapted toclose the circuit of one of said coils normally and when both of saidswitches occupy their abnormal positions, an actuating coil for one ofsaid pair of switches responsive to the current of "said machine and apair of opposing actuating coils for the other of said pair of switchesrespectively responsive to the voltage of said 'niachine and in circuitwith the other of said two actuating coils.

15. The combination with a dynamdelectric machine having a resistorassociated therewith and a plurality of switches "for controlling aportion or saidresistor, each having an actuating coil, or a relay forcontrolling said plurality of switches and having opposing actuatingcoils that are respectively energizedin accordance with the number ofswitch-actuatingcoils that are energized and the value of the voltageacross a portion of said resistor 16. The combination withadynamo-electric machine having a resistor associated therewith, of aswitch for controlling portion of said resistor and having two actuatingcoils, and aswitch for controlling the circuit of one of said coils andhaving a pair of actuating coils respectively in circuit with the otherlof said two coils and connected across a portion of said resistor.

17. The combination with a pair as dynamo-electric machines each havinga res1stor associated therew1th, of a switch for controlling each ofsaid resistors and each .having a pair of actuating coils, both oi.

which, coils must be energized to efiect the operation of thecorresponding switch, means for closing the circuits of one coil of eachoi said switches, and means controlled by' one of said switches forclosing the other coil of said other switch.

18. The combination with a dynamo-sled n said pairof switches and havingopposing actuating coils. each in circuit with one cl" said pair ofswitches.-

20. The combination with a pair ct dynamo-electric machines each havinga resistor associated therewith, of a switch for controlling each ofsaid resistors, and interlocking means controlled by each of saidswitches for insuring their successive operation.

21. The combination with a pair of dynamo electric machines each havinga re s'istor associated therewith, of a switch for controlling each ofsaid resistors and each having an actuating coil, means controlled byone of said switches for closing the circuit of the coil of said otherswitch when said one switch occupies an inoperative position, a switchfor controlling the flow of current through the resistor which iscontrolled by said one switch, and means controlled by said controllingswitch for clos ing the circuit of the coil of said one switch.

In testimony whereof, I have hereunto subscribed my name this 29th dayof May,

EDWIN S. LAMMERS, JR.

